<?php
/**
 * CDbSchema class file.
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @link http://www.yiiframework.com/
 * @copyright Copyright &copy; 2008-2011 Yii Software LLC
 * @license http://www.yiiframework.com/license/
 */

/**
 * CDbSchema is the base class for retrieving metadata information.
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @version $Id: CDbSchema.php 3297 2011-06-22 21:46:11Z qiang.xue $
 * @package system.db.schema
 * @since 1.0
 */
abstract class CDbSchema extends CComponent
{
    /**
     * @var array the abstract column types mapped to physical column types.
     * @since 1.1.6
     */
    public $columnTypes=array();

    private $_tableNames=array();
    private $_tables=array();
    private $_connection;
    private $_builder;
    private $_cacheExclude=array();

    /**
     * Loads the metadata for the specified table.
     * @param string $name table name
     * @return CDbTableSchema driver dependent table metadata, null if the table does not exist.
     */
    abstract protected function loadTable($name);

    /**
     * Constructor.
     * @param CDbConnection $conn database connection.
     */
    public function __construct($conn)
    {
        $this->_connection=$conn;
        foreach($conn->schemaCachingExclude as $name)
        $this->_cacheExclude[$name]=true;
    }

    /**
     * @return CDbConnection database connection. The connection is active.
     */
    public function getDbConnection()
    {
        return $this->_connection;
    }

    /**
     * Obtains the metadata for the named table.
     * @param string $name table name
     * @return CDbTableSchema table metadata. Null if the named table does not exist.
     */
    public function getTable($name)
    {
        if(isset($this->_tables[$name]))
        return $this->_tables[$name];
        else
        {
            if($this->_connection->tablePrefix!==null && strpos($name,'{{')!==false)
            $realName=preg_replace('/\{\{(.*?)\}\}/',$this->_connection->tablePrefix.'$1',$name);
            else
            $realName=$name;

            // temporarily disable query caching
            if($this->_connection->queryCachingDuration>0)
            {
                $qcDuration=$this->_connection->queryCachingDuration;
                $this->_connection->queryCachingDuration=0;
            }

            if(!isset($this->_cacheExclude[$name]) && ($duration=$this->_connection->schemaCachingDuration)>0 && $this->_connection->schemaCacheID!==false && ($cache=Yii::app()->getComponent($this->_connection->schemaCacheID))!==null)
            {
                $key='yii:dbschema'.$this->_connection->connectionString.':'.$this->_connection->username.':'.$name;
                if(($table=$cache->get($key))===false)
                {
                    $table=$this->loadTable($realName);
                    if($table!==null)
                    $cache->set($key,$table,$duration);
                }
                $this->_tables[$name]=$table;
            }
            else
            $this->_tables[$name]=$table=$this->loadTable($realName);

            if(isset($qcDuration))  // re-enable query caching
            $this->_connection->queryCachingDuration=$qcDuration;

            return $table;
        }
    }

    /**
     * Returns the metadata for all tables in the database.
     * @param string $schema the schema of the tables. Defaults to empty string, meaning the current or default schema.
     * @return array the metadata for all tables in the database.
     * Each array element is an instance of {@link CDbTableSchema} (or its child class).
     * The array keys are table names.
     * @since 1.0.2
     */
    public function getTables($schema='')
    {
        $tables=array();
        foreach($this->getTableNames($schema) as $name)
        {
            if(($table=$this->getTable($name))!==null)
            $tables[$name]=$table;
        }
        return $tables;
    }

    /**
     * Returns all table names in the database.
     * @param string $schema the schema of the tables. Defaults to empty string, meaning the current or default schema.
     * If not empty, the returned table names will be prefixed with the schema name.
     * @return array all table names in the database.
     * @since 1.0.2
     */
    public function getTableNames($schema='')
    {
        if(!isset($this->_tableNames[$schema]))
        $this->_tableNames[$schema]=$this->findTableNames($schema);
        return $this->_tableNames[$schema];
    }

    /**
     * @return CDbCommandBuilder the SQL command builder for this connection.
     */
    public function getCommandBuilder()
    {
        if($this->_builder!==null)
        return $this->_builder;
        else
        return $this->_builder=$this->createCommandBuilder();
    }

    /**
     * Refreshes the schema.
     * This method resets the loaded table metadata and command builder
     * so that they can be recreated to reflect the change of schema.
     */
    public function refresh()
    {
        if(($duration=$this->_connection->schemaCachingDuration)>0 && $this->_connection->schemaCacheID!==false && ($cache=Yii::app()->getComponent($this->_connection->schemaCacheID))!==null)
        {
            foreach(array_keys($this->_tables) as $name)
            {
                if(!isset($this->_cacheExclude[$name]))
                {
                    $key='yii:dbschema'.$this->_connection->connectionString.':'.$this->_connection->username.':'.$name;
                    $cache->delete($key);
                }
            }
        }
        $this->_tables=array();
        $this->_tableNames=array();
        $this->_builder=null;
    }

    /**
     * Quotes a table name for use in a query.
     * If the table name contains schema prefix, the prefix will also be properly quoted.
     * @param string $name table name
     * @return string the properly quoted table name
     * @see quoteSimpleTableName
     */
    public function quoteTableName($name)
    {
        if(strpos($name,'.')===false)
        return $this->quoteSimpleTableName($name);
        $parts=explode('.',$name);
        foreach($parts as $i=>$part)
        $parts[$i]=$this->quoteSimpleTableName($part);
        return implode('.',$parts);

    }

    /**
     * Quotes a simple table name for use in a query.
     * A simple table name does not schema prefix.
     * @param string $name table name
     * @return string the properly quoted table name
     * @since 1.1.6
     */
    public function quoteSimpleTableName($name)
    {
        return "'".$name."'";
    }

    /**
     * Quotes a column name for use in a query.
     * If the column name contains prefix, the prefix will also be properly quoted.
     * @param string $name column name
     * @return string the properly quoted column name
     * @see quoteSimpleColumnName
     */
    public function quoteColumnName($name)
    {
        if(($pos=strrpos($name,'.'))!==false)
        {
            $prefix=$this->quoteTableName(substr($name,0,$pos)).'.';
            $name=substr($name,$pos+1);
        }
        else
        $prefix='';
        return $prefix . ($name==='*' ? $name : $this->quoteSimpleColumnName($name));
    }

    /**
     * Quotes a simple column name for use in a query.
     * A simple column name does not contain prefix.
     * @param string $name column name
     * @return string the properly quoted column name
     * @since 1.1.6
     */
    public function quoteSimpleColumnName($name)
    {
        return '"'.$name.'"';
    }

    /**
     * Compares two table names.
     * The table names can be either quoted or unquoted. This method
     * will consider both cases.
     * @param string $name1 table name 1
     * @param string $name2 table name 2
     * @return boolean whether the two table names refer to the same table.
     */
    public function compareTableNames($name1,$name2)
    {
        $name1=str_replace(array('"','`',"'"),'',$name1);
        $name2=str_replace(array('"','`',"'"),'',$name2);
        if(($pos=strrpos($name1,'.'))!==false)
        $name1=substr($name1,$pos+1);
        if(($pos=strrpos($name2,'.'))!==false)
        $name2=substr($name2,$pos+1);
        if($this->_connection->tablePrefix!==null)
        {
            if(strpos($name1,'{')!==false)
            $name1=$this->_connection->tablePrefix.str_replace(array('{','}'),'',$name1);
            if(strpos($name2,'{')!==false)
            $name2=$this->_connection->tablePrefix.str_replace(array('{','}'),'',$name2);
        }
        return $name1===$name2;
    }

    /**
     * Resets the sequence value of a table's primary key.
     * The sequence will be reset such that the primary key of the next new row inserted
     * will have the specified value or 1.
     * @param CDbTableSchema $table the table schema whose primary key sequence will be reset
     * @param mixed $value the value for the primary key of the next new row inserted. If this is not set,
     * the next new row's primary key will have a value 1.
     * @since 1.1
     */
    public function resetSequence($table,$value=null)
    {
    }

    /**
     * Enables or disables integrity check.
     * @param boolean $check whether to turn on or off the integrity check.
     * @param string $schema the schema of the tables. Defaults to empty string, meaning the current or default schema.
     * @since 1.1
     */
    public function checkIntegrity($check=true,$schema='')
    {
    }

    /**
     * Creates a command builder for the database.
     * This method may be overridden by child classes to create a DBMS-specific command builder.
     * @return CDbCommandBuilder command builder instance
     */
    protected function createCommandBuilder()
    {
        return new CDbCommandBuilder($this);
    }

    /**
     * Returns all table names in the database.
     * This method should be overridden by child classes in order to support this feature
     * because the default implementation simply throws an exception.
     * @param string $schema the schema of the tables. Defaults to empty string, meaning the current or default schema.
     * If not empty, the returned table names will be prefixed with the schema name.
     * @return array all table names in the database.
     * @since 1.0.2
     */
    protected function findTableNames($schema='')
    {
        throw new CDbException(Yii::t('yii','{class} does not support fetching all table names.',
        array('{class}'=>get_class($this))));
    }

    /**
     * Converts an abstract column type into a physical column type.
     * The conversion is done using the type map specified in {@link columnTypes}.
     * These abstract column types are supported (using MySQL as example to explain the corresponding
     * physical types):
     * <ul>
     * <li>pk: an auto-incremental primary key type, will be converted into "int(11) NOT NULL AUTO_INCREMENT PRIMARY KEY"</li>
     * <li>string: string type, will be converted into "varchar(255)"</li>
     * <li>text: a long string type, will be converted into "text"</li>
     * <li>integer: integer type, will be converted into "int(11)"</li>
     * <li>boolean: boolean type, will be converted into "tinyint(1)"</li>
     * <li>float: float number type, will be converted into "float"</li>
     * <li>decimal: decimal number type, will be converted into "decimal"</li>
     * <li>datetime: datetime type, will be converted into "datetime"</li>
     * <li>timestamp: timestamp type, will be converted into "timestamp"</li>
     * <li>time: time type, will be converted into "time"</li>
     * <li>date: date type, will be converted into "date"</li>
     * <li>binary: binary data type, will be converted into "blob"</li>
     * </ul>
     *
     * If the abstract type contains two or more parts separated by spaces (e.g. "string NOT NULL"), then only
     * the first part will be converted, and the rest of the parts will be appended to the conversion result.
     * For example, 'string NOT NULL' is converted to 'varchar(255) NOT NULL'.
     * @param string $type abstract column type
     * @return string physical column type.
     * @since 1.1.6
     */
    public function getColumnType($type)
    {
        if(isset($this->columnTypes[$type]))
        return $this->columnTypes[$type];
        else if(($pos=strpos($type,' '))!==false)
        {
            $t=substr($type,0,$pos);
            return (isset($this->columnTypes[$t]) ? $this->columnTypes[$t] : $t).substr($type,$pos);
        }
        else
        return $type;
    }

    /**
     * Builds a SQL statement for creating a new DB table.
     *
     * The columns in the new  table should be specified as name-definition pairs (e.g. 'name'=>'string'),
     * where name stands for a column name which will be properly quoted by the method, and definition
     * stands for the column type which can contain an abstract DB type.
     * The {@link getColumnType} method will be invoked to convert any abstract type into a physical one.
     *
     * If a column is specified with definition only (e.g. 'PRIMARY KEY (name, type)'), it will be directly
     * inserted into the generated SQL.
     *
     * @param string $table the name of the table to be created. The name will be properly quoted by the method.
     * @param array $columns the columns (name=>definition) in the new table.
     * @param string $options additional SQL fragment that will be appended to the generated SQL.
     * @return string the SQL statement for creating a new DB table.
     * @since 1.1.6
     */
    public function createTable($table, $columns, $options=null)
    {
        $cols=array();
        foreach($columns as $name=>$type)
        {
            if(is_string($name))
            $cols[]="\t".$this->quoteColumnName($name).' '.$this->getColumnType($type);
            else
            $cols[]="\t".$type;
        }
        $sql="CREATE TABLE ".$this->quoteTableName($table)." (\n".implode(",\n",$cols)."\n)";
        return $options===null ? $sql : $sql.' '.$options;
    }

    /**
     * Builds a SQL statement for renaming a DB table.
     * @param string $table the table to be renamed. The name will be properly quoted by the method.
     * @param string $newName the new table name. The name will be properly quoted by the method.
     * @return string the SQL statement for renaming a DB table.
     * @since 1.1.6
     */
    public function renameTable($table, $newName)
    {
        return 'RENAME TABLE ' . $this->quoteTableName($table) . ' TO ' . $this->quoteTableName($newName);
    }

    /**
     * Builds a SQL statement for dropping a DB table.
     * @param string $table the table to be dropped. The name will be properly quoted by the method.
     * @return string the SQL statement for dropping a DB table.
     * @since 1.1.6
     */
    public function dropTable($table)
    {
        return "DROP TABLE ".$this->quoteTableName($table);
    }

    /**
     * Builds a SQL statement for truncating a DB table.
     * @param string $table the table to be truncated. The name will be properly quoted by the method.
     * @return string the SQL statement for truncating a DB table.
     * @since 1.1.6
     */
    public function truncateTable($table)
    {
        return "TRUNCATE TABLE ".$this->quoteTableName($table);
    }

    /**
     * Builds a SQL statement for adding a new DB column.
     * @param string $table the table that the new column will be added to. The table name will be properly quoted by the method.
     * @param string $column the name of the new column. The name will be properly quoted by the method.
     * @param string $type the column type. The {@link getColumnType} method will be invoked to convert abstract column type (if any)
     * into the physical one. Anything that is not recognized as abstract type will be kept in the generated SQL.
     * For example, 'string' will be turned into 'varchar(255)', while 'string not null' will become 'varchar(255) not null'.
     * @return string the SQL statement for adding a new column.
     * @since 1.1.6
     */
    public function addColumn($table, $column, $type)
    {
        $type=$this->getColumnType($type);
        $sql='ALTER TABLE ' . $this->quoteTableName($table)
        . ' ADD ' . $this->quoteColumnName($column) . ' '
        . $this->getColumnType($type);
        return $sql;
    }

    /**
     * Builds a SQL statement for dropping a DB column.
     * @param string $table the table whose column is to be dropped. The name will be properly quoted by the method.
     * @param string $column the name of the column to be dropped. The name will be properly quoted by the method.
     * @return string the SQL statement for dropping a DB column.
     * @since 1.1.6
     */
    public function dropColumn($table, $column)
    {
        return "ALTER TABLE ".$this->quoteTableName($table)
        ." DROP COLUMN ".$this->quoteColumnName($column);
    }

    /**
     * Builds a SQL statement for renaming a column.
     * @param string $table the table whose column is to be renamed. The name will be properly quoted by the method.
     * @param string $name the old name of the column. The name will be properly quoted by the method.
     * @param string $newName the new name of the column. The name will be properly quoted by the method.
     * @return string the SQL statement for renaming a DB column.
     * @since 1.1.6
     */
    public function renameColumn($table, $name, $newName)
    {
        return "ALTER TABLE ".$this->quoteTableName($table)
        . " RENAME COLUMN ".$this->quoteColumnName($name)
        . " TO ".$this->quoteColumnName($newName);
    }

    /**
     * Builds a SQL statement for changing the definition of a column.
     * @param string $table the table whose column is to be changed. The table name will be properly quoted by the method.
     * @param string $column the name of the column to be changed. The name will be properly quoted by the method.
     * @param string $type the new column type. The {@link getColumnType} method will be invoked to convert abstract column type (if any)
     * into the physical one. Anything that is not recognized as abstract type will be kept in the generated SQL.
     * For example, 'string' will be turned into 'varchar(255)', while 'string not null' will become 'varchar(255) not null'.
     * @return string the SQL statement for changing the definition of a column.
     * @since 1.1.6
     */
    public function alterColumn($table, $column, $type)
    {
        $type=$this->getColumnType($type);
        return 'ALTER TABLE ' . $this->quoteTableName($table) . ' CHANGE '
        . $this->quoteColumnName($column) . ' '
        . $this->quoteColumnName($column) . ' '
        . $this->getColumnType($type);
    }

    /**
     * Builds a SQL statement for adding a foreign key constraint to an existing table.
     * The method will properly quote the table and column names.
     * @param string $name the name of the foreign key constraint.
     * @param string $table the table that the foreign key constraint will be added to.
     * @param string $columns the name of the column to that the constraint will be added on. If there are multiple columns, separate them with commas.
     * @param string $refTable the table that the foreign key references to.
     * @param string $refColumns the name of the column that the foreign key references to. If there are multiple columns, separate them with commas.
     * @param string $delete the ON DELETE option. Most DBMS support these options: RESTRICT, CASCADE, NO ACTION, SET DEFAULT, SET NULL
     * @param string $update the ON UPDATE option. Most DBMS support these options: RESTRICT, CASCADE, NO ACTION, SET DEFAULT, SET NULL
     * @return string the SQL statement for adding a foreign key constraint to an existing table.
     * @since 1.1.6
     */
    public function addForeignKey($name, $table, $columns, $refTable, $refColumns, $delete=null, $update=null)
    {
        $columns=preg_split('/\s*,\s*/',$columns,-1,PREG_SPLIT_NO_EMPTY);
        foreach($columns as $i=>$col)
        $columns[$i]=$this->quoteColumnName($col);
        $refColumns=preg_split('/\s*,\s*/',$refColumns,-1,PREG_SPLIT_NO_EMPTY);
        foreach($refColumns as $i=>$col)
        $refColumns[$i]=$this->quoteColumnName($col);
        $sql='ALTER TABLE '.$this->quoteTableName($table)
        .' ADD CONSTRAINT '.$this->quoteColumnName($name)
        .' FOREIGN KEY ('.implode(', ', $columns).')'
        .' REFERENCES '.$this->quoteTableName($refTable)
        .' ('.implode(', ', $refColumns).')';
        if($delete!==null)
        $sql.=' ON DELETE '.$delete;
        if($update!==null)
        $sql.=' ON UPDATE '.$update;
        return $sql;
    }

    /**
     * Builds a SQL statement for dropping a foreign key constraint.
     * @param string $name the name of the foreign key constraint to be dropped. The name will be properly quoted by the method.
     * @param string $table the table whose foreign is to be dropped. The name will be properly quoted by the method.
     * @return string the SQL statement for dropping a foreign key constraint.
     * @since 1.1.6
     */
    public function dropForeignKey($name, $table)
    {
        return 'ALTER TABLE '.$this->quoteTableName($table)
        .' DROP CONSTRAINT '.$this->quoteColumnName($name);
    }

    /**
     * Builds a SQL statement for creating a new index.
     * @param string $name the name of the index. The name will be properly quoted by the method.
     * @param string $table the table that the new index will be created for. The table name will be properly quoted by the method.
     * @param string $column the column(s) that should be included in the index. If there are multiple columns, please separate them
     * by commas. Each column name will be properly quoted by the method, unless a parenthesis is found in the name.
     * @param boolean $unique whether to add UNIQUE constraint on the created index.
     * @return string the SQL statement for creating a new index.
     * @since 1.1.6
     */
    public function createIndex($name, $table, $column, $unique=false)
    {
        $cols=array();
        $columns=preg_split('/\s*,\s*/',$column,-1,PREG_SPLIT_NO_EMPTY);
        foreach($columns as $col)
        {
            if(strpos($col,'(')!==false)
            $cols[]=$col;
            else
            $cols[]=$this->quoteColumnName($col);
        }
        return ($unique ? 'CREATE UNIQUE INDEX ' : 'CREATE INDEX ')
        . $this->quoteTableName($name).' ON '
        . $this->quoteTableName($table).' ('.implode(', ',$cols).')';
    }

    /**
     * Builds a SQL statement for dropping an index.
     * @param string $name the name of the index to be dropped. The name will be properly quoted by the method.
     * @param string $table the table whose index is to be dropped. The name will be properly quoted by the method.
     * @return string the SQL statement for dropping an index.
     * @since 1.1.6
     */
    public function dropIndex($name, $table)
    {
        return 'DROP INDEX '.$this->quoteTableName($name).' ON '.$this->quoteTableName($table);
    }
}
